There is known, in particular from the document FR-2 807 558, a hand-actuated pipette for moving a piston in the pipette with a view to sampling a liquid and subsequently ejecting this liquid. The pipette comprises means of adjusting the value of the volume of liquid to be sampled and an electronic screen 12 for displaying this value.
It is possible to calibrate this pipette by recording in the pipette control microprocessor a calibration value corresponding to a predetermined mechanical configuration of the adjustment means. The pipette comprises one or more brushes traveling over one or more tracks having increments and connected to the volume adjustment means. When the user modifies the adjustment of the volume to be sampled, the brush or brushes travel over the increments in the tracks and the microprocessor counts the number of increments traveled, which enables it to display the new volume value corresponding to the adjustment obtained.
Nevertheless, one drawback is that, if the user modifies the adjustment of the volume when the electronic part of the pipette is not supplied with current (the pipette being switched off or the energy source being exhausted), the pipette loses count of the increments traveled. The pipette, when it is once again supplied with energy, is then no longer in a position to display a correct value corresponding to the volume adjustment obtained.
One aim of the invention is to mitigate this drawback by making it possible to display a correct volume value to be sampled, even if the volume adjustment means is manipulated while the pipette is not supplied with power.